Waste Water Lifting System

ABSTRACT

A waste water lifting system with a collecting tank ( 2 ) for liquids, in particular waste water, fecal matter, or the like, and with a device for emptying the tank, in particular a pump ( 3 ) which is connected to a motor and is arranged as a motor and pump unit in an entirely or partially recessed manner in the tank ( 2 ). The tank ( 2 ) has at least one inlet and outlet pipe ( 4, 5 ) for the liquids, and the waste water lifting system is provided with a device for switching the pump ( 2 ) on and off as a function of the liquid level (PA, PE, A) within the tank ( 2 ). The tank floor ( 12 ) or at least a partial surface thereof ( 12.1, 12.2 ) is constructed to be elastically flexible as a function of the filling level of the tank. One or more sensors ( 15 ) are arranged on the outside ( 14 ) of the elastically flexible tank floor surface ( 12.1, 12.2 ) and measure the deformation thereof. The elastically flexible tank floor part ( 12.1, 12.2 ) is arranged at a distance from an installation surface ( 13 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of international patent application no. PCT/EP2006/011966, filed Dec. 13, 2006, designating the United States of America, and published in German on Jun. 21, 2007 as WO 2007/068455, the entire disclosure of which is incorporated herein by reference. Priority is claimed based on Federal Republic of Germany patent application no. DE 10 2005 060 556.7, filed Dec. 17, 2005.

BACKGROUND OF THE INVENTION

The present invention relates to a waste water lifting system comprising a collecting tank for liquids, in particular sewage, excrement or the like, and comprising a device for emptying the tank, in particular a pump which is connected to a motor and which is arranged as a motor pump unit wholly or partially lowered in the tank, the tank has at least one inlet and outlet pipe, respectively, for the liquids, and the waste water lifting system is provided with a device for switching the pump as a function of a liquid level within the tank.

Waste water lifting systems of this kind are frequently used as excrement lifting systems and are employed in buildings and plants when waste water to be conveyed accrues beneath a so-called backwash level. The backwash level is usually a height level of an external waste water system, which is disposed outside a building under a road. For a proper operation of such a waste water lifting system, devices for monitoring the liquid level within the tank are necessary in order to be able to ensure that the pump is switched on and off on time.

A waste water lifting system of this type for the collection and pumping-off of sewage water is known from published German patent application no. DE 33 11 980. To this end, the waste water lifting system has a collecting tank and a motor pump unit located therein, which receives its switching signals through a pneumatic control bell. This is constituted by a Pitot tube, the air volume of which, when a tank content is raised, is enclosed and thus generates a static pressure in the Pitot tube. This pressure is registered by a pressure sensor and its value converted into a fill level height of the respective tank. However, such dynamic pressure systems, which exist in a wide variety of forms, are susceptible to the sewage water, and its constituent parts, present within the tank. Since a failure of a relevant component of this kind is of fundamental significance for the entire system and the building whose waste it disposes, considerable servicing and maintenance works are necessary to ensure the functionality thereof. In order to prevent leaks or deposits within such a Pitot tube system, the tube must constantly be cleared in a complex manner by separate control elements or the above drawbacks can be prevented by the introduction of air bubbles.

Alternatively thereto, float switches, as are known, for example, from published German patent application no. DE 3,430,527, have gained market acceptance for controlling the pump. Depending on the liquid level within the tank, a float-actuated switch triggers the necessary switch-on and switch-off motions of a pump. These float switches also, however, are restricted or jeopardized in terms of their function by deposits or solid constituents in the liquid.

SUMMARY OF THE INVENTION

Against this background, it is an object of the present invention to provide a level registration system by which the fill level in the tank can be reliably registered without difficulty.

A further object of the invention is to provide a level registrations system which does not require use of complex, additional protective devices exposed to the liquid.

These and other objects have been achieved in accordance with the present invention by providing a waste water lifting system comprising a collecting tank for a liquid, the tank having at least one inlet and an outlet for the liquid; a device for emptying the tank; and a device for switching the tank emptying device on or off as a function of a liquid level within the tank; in which the tank comprises at least a partial area which is elastically resiliently deformable as a function of the liquid level in said tank, and at least one sensor is disposed on the outside of the tank for measuring deformation of the deformable tank area, the at least one sensor being operatively connected to the switching device for transmitting a measured deformation of the deformable tank area to the switching device as an indication of the liquid level in said tank.

Thus, in accordance with the present invention, the tank floor, or at least a part-area of the tank floor, may be configured such that it is elastically resilient as a function of the tank fill level, and one or more sensors are disposed on the outer side of the elastically resilient tank floor area and measure the deformation thereof.

With this arrangement, the problem of fill level sensors becoming contaminated is avoided. Since the sensors which register the degree of deformation of a tank floor part are fitted on the outer side of the tank, they are fully removed from the harmful influences of the waste water. As a result of the arrangement of the tank floor part at a distance from an installation area for the waste water lifting system, a cavity is formed therebetween. This cavity is simultaneously a protective space for the external sensors against external mechanical influences and prevents damage to the elastically resilient tank floor part.

The tank floor or a part-area thereof is designed such that at least one sensor is disposed at a tank floor measuring point at which an evaluable deformation occurs when the tank is maximally filled. Similarly, it is provided that at least one sensor is disposed at a tank floor measuring point at which an evaluable deformation occurs when the tank is minimally filled. The generation of sensor signals, with which the necessary switch-on, switch-off or alarm points of a waste water lifting system, or of the pump connected thereto, and the dependence on the respective fill level in the tank, can be reliably registered, is thus ensured. The deformation of load-imposing tank, which deformation here maximally occurs at a measuring point, lies within the respectively permitted material values. This is achieved by an appropriate shaping of the tank floor or of a part thereof.

It is likewise possible to arrange an elastically resilient element in a leaktight and flexibly held manner in the tank floor and to connect it to at least one sensor. A sensor signal above a respective fill level is processed by the evaluation units (known per se) of such waste water lifting systems for a pump control system.

According to another embodiment, one or more sensors are exchangeably fastened. This can be effected by simple snap-fastening or by using clamping connections and simplifies manufacture, while at the same time making a sensor easy to exchange in a possible service.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawing figures, in which:

FIG. 1 is an installation diagram for a waste water lifting system;

FIG. 2 is a view of a conventional waste water lifting system;

FIG. 3 is a view of a first illustrative sensor arrangement according to the present invention;

FIG. 4 is a view of a second illustrative sensor arrangement according to the invention, and

FIG. 5 is an enlarged representation of a tank floor constructed in accordance with the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In FIG. 1, a cross section through a building is shown, in the basement of which a sanitary device is represented. Sewage from the sanitary device and other liquids to be disposed of flow to a waste water lifting system 1 and are collected therein until a sufficiently high fill level for an ad hoc conveyance is reached. The waste water lifting system 1 comprises a liquid-tight and odor-tight tank 2 and a pump 3, disposed sealingly therein, in the form of a motor pump unit, which is designed for the smooth-running conveyance of such liquids. Via an inlet pipe 4, accrued waste water is led into the tank 2, and via an outlet pipe 5 in the form of a pressure line, is conveyed over a backwash level 6 in order to flow from there into a sewage system 7. In general, such a tank 2 is provided with a ventilation (not represented here), whereby a gas evacuation is achieved and the creation of an overpressure in the tank 2 is prevented. Such a ventilation port is generally run over the roof of a building in order to prevent odors from causing a nuisance.

FIG. 2 is an enlarged side view representation of a waste water lifting system according to the prior art. The tank 2 which collects the sewage is hermetically sealed in order to prevent its escape and prevent odor nuisances within a building. The tank 2 is connected to an inlet line 4 and to an outlet line 5, in which a non-return valve 8 and a shut-off valve 9 are disposed. Partially immersed in the tank 2 is an electrically driven pump 3. It pumps into the outlet pipe 5 and is only switched on when needed. To this end, it is connected to a switching apparatus 10 for controlling and monitoring the operation of such a waste water lifting system.

By way of example, a float switch 11 is shown in broken lines as a representation of the prior art. Such a float switch disposed within the tank 2 is used to transmit a signal to the switching apparatus 10 when three tank fill levels P_(A), P_(E) and A (shown in dash-dot representation) are reached, and from said switching apparatus a switching function for the waste water lifting system is triggered. The lowermost line P_(A) here stands for the switching function “pump off”. The pivotably mounted float switch then hangs down. As the liquid level increases, the float moves upwards until, at a tank fill level P_(E), it reaches a switching setting corresponding to the switching function “pump on” and causes the pump to be switched on by the switching apparatus 10. And when the uppermost, third tank fill level A is reached, a non-permitted operating state, an alarm function is triggered. If a greater quantity of waste water flows into the tank than can be pumped away by the pump, then the alarm function prevents the cellar rooms from being flooded by a backflow and prevents waste water from escaping from the inlets of the connected-up devices. This state can also arise in the event of a pump failure. Care must therefore be taken to ensure that such a float switch disposed within the tank is constantly ready for use.

In contrast, FIG. 3 shows as an improvement to the prior solutions an enlarged detail of a tank 2 in the form of a cross-section through a tank floor 12. Tank floor 12 has a partial-region 12.1, which is disposed above and at a distance from a mounting plane 13. As a result, a wholly or partially closed-off cavity 16 is formed between the mounting plane 13 and the floor area 12 of the tank 2 resting thereon. This shields the resilient partial-region 12.1 of the tank floor from external influences. The partial-region 12.1 of the tank floor 12 has an elastically resilient construction, and at least one sensor 15 is disposed on the outer side 14 thereof. The distance between the sensor 15 mounted at the lowest point and the mounting plane 13 preferably is dimensioned such that, when tank 2 is fully filled, contact between the sensor and the mounting plane is safely prevented.

The respective degree of filling of a tank 2 acts, in the form of a column of liquid, deformingly upon the elastically resiliently configured partial-area 12.1. The respective degree of deformation thereof is registered by at least one external sensor 15. Its signal is converted with the aid of the switching apparatus 10 into a fill level signal, is displayed and/or is used to control the pump 3. Due to a liquid level which is reached within the tank and due to the column of liquid resulting therefrom, the tank floor area is deformed or deflected differently. The orders of magnitude of these deformations lie within the permitted values of the material respectively used for the tank 2. The sensor 15 is thus affected by the deformation such that the output of the sensor can be as a direct measure of the fill level within the tank 2. Since the sensor 15 is disposed in a cavity 16, formed between the mounting plane 13 and floor part 12.1, which is elevated relative to the mounting plane, an additional protective space for the sensor 15 is obtained. The signal lines (not shown here) of the sensor 15 are likewise located completely outside the waste water lifting system and can therefore be connected to the switching apparatus 10 without difficulty. The hitherto usual pipe bushings in the tank 2 can be entirely omitted. This constitutes an additional safety feature for a safe operation.

FIG. 4 shows another embodiment of the floor area 12. Here, in the resilient tank floor part 12.1, a tank floor part 12.2 of elastically resilient configuration is additionally designed as a membrane inserted in a liquid-tight manner. This tank floor part 12.2 can consist of a rubber material, can be configured as plate consisting of an elastic plastics material, can be designed as a metallic membrane or as a combination of such materials. The respective liquid level in the tank 2 deflects the tank floor part 12.2 in the direction of the outer side 14. A sensor 15 disposed on the outer side 14 and operatively connected to the tank floor part 12.2 generates a sensor signal from the deflection.

FIG. 5 shows the arrangement of the sensor 15 in an exchangeably designed housing 17, which with known means 18 can be fastened to the tank floor part 12.1. In the shown illustrative embodiment, it serves simultaneously to fasten the tank floor part 12.2. And the sensor 15 can be designed as an inductive system for a path measurement or as a piezoquartz sensor for a pressure measurement.

The foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting. Since modifications of the described embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed broadly to include all variations within the scope of the appended claims and equivalents thereof. 

1. A waste water lifting system comprising: a collecting tank for a liquid, said tank having at least one inlet and an outlet for the liquid; a device for emptying the tank; and a device for switching the tank emptying device on or off as a function of a liquid level within the tank; wherein said tank comprises at least a partial area which is elastically resiliently deformable as a function of the liquid level in said tank; and at least one sensor is disposed on the outside of the tank for measuring deformation of the deformable tank area, said at least one sensor being operatively connected to the switching device for transmitting a measured deformation of the deformable tank area to the switching device as an indication of the liquid level in said tank.
 2. A system as claimed in claim 1, wherein said liquid is sewage.
 3. A system as claimed in claim 1, wherein said device for emptying the tank comprises a pump and motor unit.
 4. A system as claimed in claim 3, wherein said pump and motor unit is disposed at least partially within the tank.
 5. A system as claimed in claim 4, wherein said pump and motor unit is disposed entirely within said tank.
 6. A system as claimed in claim 1, wherein said deformable tank area is a partial area of the tank floor.
 7. A system as claimed in claim 6, wherein said tank is disposed on an installation area, and the deformable tank floor area is spaced a distance from said installation area.
 8. A system as claimed in claim 6, wherein said at least one sensor is disposed at a tank floor measuring point at which an evaluable deformation occurs when the tank is maximally filled.
 9. A system as claimed in claim 6, wherein said at least one sensor is disposed at a tank floor measuring point at which an evaluable deformation occurs when the tank is minimally filled.
 10. A system as claimed in claim 6, wherein an elastically resilient element is arranged in the tank floor in a leaktight and flexibly held manner and is connected to said at least one sensor.
 11. A system as claimed in claim 1, wherein said at least one sensor is releasably secured to the outside of the tank, whereby said at least one sensor can be exchanged for another sensor. 